Comet Pan-STARRS (C/2011 L4), widely expected to become a naked-eye object in early March, is now closer to the sun than Venus. Solar heating is vaporizing the comet's icy core and creating a wide, fan-shaped tail visible through binoculars in the southern hemisphere. Ignacio Diaz Bobillo sends this picture from Buenos Aires, Argentina:

"I saw Comet Pan-STARRS just before daybreak in the constellation Grus," says Bobillo. "This is what it looked like through a small telescope, imaged with an exposure time of 8x2 minutes." In early March, Comet Pan-STARRS will make its closest approach to the sun inside the orbit of Mercury; at that time it could brighten to easy naked-eye visibility. No one knows exactly what will happen, however, because it is a fresh comet being exposed to solar heating for the first time. Experts discuss the possibilities in this video from Science@NASA. More:3D orbit, ephemeris, light curves, NASA story. www.spaceweather.com